Physiological and Morphological Studies on Characteristics of Nociceptive Primary Afferent Neurons (Polymodal Receptors).

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1. In order to clarify changes in polymodal receptor activities in inflammation, effects of inflammatory mediators on the heat response of testicular polymodal receptors were studied in vitro using testis-spermatic nerve preparations. ProstaglandinE_2 augmented the heat responses from the concentration 100 times higher than that needed to augment the Bradykinin (BK) response. 5-HT augmented both responses in the same range of concentration. Histamine (His) had different effects : His suppressed or augmented the BK response depending on whether His induced substantial increase in discharge rate or not, whereas it always augmented the heat response. BK augmented the heat response. None of these mediators could augment the heat response so strong as 55^ﾟC-30s heat stimulation did. BK response was revealed to be mediated by B2 type receptor. 2. Peripheral structure of identified testicular polymodal receptors was clarified by EM. Spinal termination of identified testicular polymodal receptors was traced mainly in lamina I by intracellular injection of PHA-L. Double labeling with fluorescent dyes revealed that more than 90% DRG neurons innervating the testis contained CGRP. 3. Nervous component in changes in intraocular pressure induced by inflammatory mediators was clarified, but the possibility for substance P to be its neuronal mediator was not supported.